The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Torrefaction and pyrolysis processes are known to convert biomass into combustible fuel, called “charcoal” or “biocoal”. The torrefaction process involves a thermo-chemical treatment of biomass in the absence of oxygen at 200° C. to 280° C. and under atmospheric pressure. The pyrolysis process involves rapid heating of biomass at 700° C. to 1000° C. or above and generally at high pressure. The charcoal generated from the torrefaction process or pyrolysis process may be used in existing coal-fired power plants as regular charcoal (called “ecocoal”), as a soil amendment (called “biochar”), or as a filtration agent (called “activated carbon”).
The torrefaction process is more cost-effective due to a relatively low temperature and pressure involved. The charcoal generated by the conventional torrefaction process, however, does not have a desired grindability and moisture content suitable for use in the power plants, which generally use pulverized coal with particle size less than 0.2 mm.
Moreover, conventional torrefaction or pyrolysis processes incur significant costs prior to and after the torrefaction or pydrolysis processes, in addition to the costs for converting biomass into charcoal. For example, the biomass needs to be pre-processed and transported to the torrefaction or pyrolysis facility. Pre-processing the biomass includes chipping or pelletizing the biomass to reduce the size of the raw biomass and pre-heating the biomass to reduce the water content. Additional costs are also incurred in transporting large amount of biomass from the biomass sources to the torrefaction facility/site and transporting the charcoal from the torrefaction facility/site to a commercial destination. In view of the additional costs incurred, the charcoal manufactured from the conventional torrefaction process may not be economically feasible for commercial use.